Minimum safety speed for the Boeing 747

Recommended Posts

I would like to ask those who fly the Boeing 747 what the minimum safety speed (True airspeed /ground speed) is? I feel minimum speed would be 200 knots as below that speed say at 190 knots is dangerously low as I am tending to stall. I did a flight and just before intercepting the ILS I lowered the landing gear and lowered the flaps 3 notches and reduced speed by the speed hold button (autopilot) to 190 and the 747 would not take it as it took the turn to align the ILS beam and it stalled and crashed!RegardsShri

Share this post

Link to post

Share on other sites

Too many variables Are you flying the default 747 that came with FSX?1. What is the weight of the aircraft (depending on whats on it including amount of fuel)2. What is the landing configuration? Flaps. what is your flap setting? 25?3. If you use the FMC Computer (Addons like PMDG 747) would compute and give you the precise speed.assuming you have like 20% fuel or thereabouts left and you have 25degree flaps, you approximate speed should be at 150-170Nowhere near 190 or 200.Also.. what matters is Indicated Air speed. Not True airspeed or Ground speed. If the Indicated Air speed drops below certain speed for a particular aircraft in a particular configuration, it would stall. The approach speed should be around 1.3 times that stall speed.Hope that helpsMannyPS: You may want to fly smaller aircrafts before flying the heavies. Just a thought.

Share this post

Link to post

Share on other sites

Thanks Manny for your reply. I flew the default 747 'as it is' and fuel at the time of the final procedure was 91%. I flew default 747 the way it loaded off the DVD without any change so the weight of the aircraft is known to you even though I am unable to calculate it. So now the variables are limited and that is the fuel which is 91% and the aircraft stalled at indicated airspeed 190knots at height of less than 3000 AGL with landing gear down and flaps 3 notches down.Do you have any knowledge for a calculator which would calculate precisely the speeds?Further digressing from the main point, you mentioned about indicated airspeed. I believe ground speed or true airspeed is what is wanted and indicated airspeed is 'false' as it depends on the air density, which can give absurdly low values when flying high altitudesThanks RegardsShri

Share this post

Link to post

Share on other sites

Thanks Manny for your reply. I flew the default 747 'as it is' and fuel at the time of the final procedure was 91%. I flew default 747 the way it loaded off the DVD without any change so the weight of the aircraft is known to you even though I am unable to calculate it. So now the variables are limited and that is the fuel which is 91% and the aircraft stalled at indicated airspeed 190knots at height of less than 3000 AGL with landing gear down and flaps 3 notches down.Do you have any knowledge for a calculator which would calculate precisely the speeds?Further digressing from the main point, you mentioned about indicated airspeed. I believe ground speed or true airspeed is what is wanted and indicated airspeed is 'false' as it depends on the air density, which can give absurdly low values when flying high altitudesThanks RegardsShri

Share this post

Link to post

Share on other sites

Thanks Manny for your reply. I flew the default 747 'as it is' and fuel at the time of the final procedure was 91%. I flew default 747 the way it loaded off the DVD without any change so the weight of the aircraft is known to you even though I am unable to calculate it. So now the variables are limited and that is the fuel which is 91% and the aircraft stalled at indicated airspeed 190knots at height of less than 3000 AGL with landing gear down and flaps 3 notches down.Do you have any knowledge for a calculator which would calculate precisely the speeds?Further digressing from the main point, you mentioned about indicated airspeed. I believe ground speed or true airspeed is what is wanted and indicated airspeed is 'false' as it depends on the air density, which can give absurdly low values when flying high altitudesThanks RegardsShri

Share this post

Link to post

Share on other sites

Suggest you wikipedia airspeeds to better understand them.Your Indicated airspeed is what you fly an airplane by.Density altitude influences the true airspeed / ground speed and not the indicated airspeed. Aircraft indicated stall speed is always the same when density altitude is higher or lower. Density altitude influences the true airspeed / ground speed and not the indicated airspeed.

Share this post

Link to post

Share on other sites

.. and besides which (assuming -400 version) - if you're flying at full capacity minus 9% fuel, your landing weight is going to be around 604,844lbs... which exceeds the maximum landing weight of 574,000lbs for the domestic 747-400. This can only have a bad ending....;)

Share this post

Link to post

Share on other sites

>Further digressing from the main point, you mentioned about>indicated airspeed. I believe ground speed or true airspeed is>what is wanted and indicated airspeed is 'false' as it depends>on the air density, which can give absurdly low values when>flying high altitudesStall speed is always referenced to the indicated airspeed.IAS is the speed at which the airfoil is moving through the airmass. That is always constant, regardless of the ambient airpressure.If the stall speed is 140 KIAS at ground level, it is still 140 KIAS at FL400... ;)

Share this post

Link to post

Share on other sites

See... :)Like others here have said.. Indicated Air speed is your life and death speed. You live and die by it. Whats important is what the Aircraft thinks the speed is...not what you know the speed is in reference to your life. IAS is the speed the aircraft knows...and when that falls below certain level, it stalls. Naturally, IAS is what is in your primary instrument. Not True Air speed nor Ground speed although they are useful for YOU, its not for the aircraft.:)Manny

Share this post

Link to post

Share on other sites

Guest D17S

If you're serious about how big airplanes really work and fly (especially the 744), latch on to PMDG's 744 addon. For instance, in a real airplane, the airspeed tape will display red "bricks" on the airspeed tape. The ADC (air data computer) monitors the airplane's configurtion and weight and then presents red tiles on the airspeed tape telling you "Don't slow-down beyond here." The PMDG airplane simulates these (and most other) functions very accurately.If you really want learn how to operate a heavy jet, the PMDG 744 will get you there. For a more serious simmer, the default 744 is a toy.

Share this post

Link to post

Share on other sites

I throughly disagree. If one is really serious about flying at all, one will invest the time to completely understand it at the most basic level......without fancy-schmanzy ADC and other electronic crutches to muddy the waters.The basic principles of flight are identical for all aircraft from the most humble to the most sophisticated.Presumably that's the reason why all flight instruction begins with ground school and then progresses upwards from there... :)

Share this post

Link to post

Share on other sites

Guest D17S

However once a child has learned to walk . . . "Really Serious" also entails departing London and finding LA with more than a pint to spare. That's where we techno geeks come in. Stick and rudder was all Rittmeister Manfred Albrecht Freiherr von Richthofen had in the can. There's still that, for sure, but there's a bit more to it these days.

Share this post

Link to post

Share on other sites

>However once a child has learned to walk . . . >>"Really Serious" also entails departing London and finding LA>with more than a pint to spare. That's where we techno geeks>come in. Stick and rudder was all Rittmeister Manfred Albrecht>Freiherr von Richthofen had in the can. There's still that,>for sure, but there's a bit more to it these days. But... that is precisely my point! The OP hasn't "learned to walk" yet, but you're recommending that he jump into the Boston Marathon right away......and expect to win! :)Without the basics down cold, how well could anyone cope with an extreme emergency?

AVSIM is a free service to the flight simulation community. AVSIM is staffed completely by volunteers and all funds donated to AVSIM go directly back to supporting the community. Your donation here helps to pay our bandwidth costs, emergency funding, and other general costs that crop up from time to time. Thank you for your support!

Donation Goals

AVSIM's 2018 Fundraising Goal

Donate to our annual general fund. This donation keeps our doors open and providing you service 24 x 7 x 365. Your donation here helps to pay our bandwidth costs, emergency funding, and other general costs that crop up from time to time. We reset this goal every new year for the following year's goal.